Very interesting!! Both the link and the movntq instruction. I'll read and
study.

Thanks Tobias!!

2012/12/8 Tobias Boege [off-list ref]

On Sat, 08 Dec 2012, Gustavo da Silva wrote:

quoted

Hello Kernel Brothers!! How are you???

So, I would like test the performance of my notebook, developing one or

two

quoted

utilities, and have a better
mensurement about the speed.

But it can help all of us.

1st: I would like mensure the speed making a counter (exacly bogomips?

may

quoted

be). Loop+counter during 1 tickrate.
2nd: The most interesting: How many memory cells in ram can we
access during 1tickrate? How could we develop this?!

Both utils may run in long mode (64bits). Well, in real mode too; so, we
can compare the speed in the two modes!

Some one knows how to develop a very small program/routine about that?!

For the 2nd situation, a simple idea wrote in codesnipet form (consider

the

quoted

intention, not the sintax! there are bugs! I know. Intel syntax.)

Obviously! ;-)

quoted

  dw the_counter_cell 0
  lea bx, the_counter_cell
  xor bx,bx
label:
  inc [bx]    # Could not be so simple like this, because the address can
be cached. Right?
  loop label # breaked by an interruption. Just to express the intention.

How could we create a small code for the 2nd situation, tring to force

the

quoted

processor to not use the cache?

As Drepper says[0], use the movntq instruction on x86_64 to bypass the
cache.

Regards,
Tobi

[0] http://www.akkadia.org/drepper/cpumemory.pdf p. 47ff.


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-- 
Atenciosamente,

Gustavo da Silva
gustavodasilva at gmail.com
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